buffer i/o using read(2) on BSD sockets

[Michael I. Bushnell]

In article <85 at cvbnetPrime.COM> aperez at cvbnet.UUCP (Arturo Perez x6739) writes:

>This is one of my pet peeves about BSD sockets.  There is no way
>to read an arbitrary amount of data from a socket.  You have to be
>aware of the kernel level buffering NO MATTER WHAT LEVEL your writing
>your code at; i.e. apps, system, etc.

>Why can't the kernel block your process until you get all the data you're
>asking for (unless, of course, FIONBIO or O_NDELAY is set)?  If I'm
>willing to wait, I'm willing to wait.  And if the connection goes down during
>the transfer, I can live with that, too, just return an error.

>Why was such a silly decision made?

Nothing new.  The same is true of terminal I/O.  

All you need is:

int
myread(des, buf, buflen)
     int des, buflen
     char *buf;
{
  char *bp = buf;
  int nread = 0, nbytes;

  while (nread != buflen)
    {
      nbytes = read(des, bp, buflen - nread);
      if (nbytes == -1)
        return -1;		/* Or whatever else you want */
      bp += nbytes, nread += nbytes;
    }
}

This will solve your problem quite nicely.  Any questions?  Now you
*don't* need to know about the low-level buffering.  




--
    Michael I. Bushnell      \     This above all; to thine own self be true
LIBERTE, EGALITE, FRATERNITE  \    And it must follow, as the night the day,
   mike at unmvax.cs.unm.edu     /\   Thou canst not be false to any man.
        CARPE DIEM           /  \  Farewell:  my blessing season this in thee!